During Release 12, the LTE standard has been extended with support of device to device (D2D) communication (specified as “sidelink”) features targeting both commercial and Public Safety applications. Some applications enabled by Rel-12 LTE are device discovery, where devices are able to sense the proximity of another device and associated application by broadcasting and detecting discovery messages that carry device and application identities. Another application consists of direct communication based on physical channels terminated directly between devices.
One of the potential extensions for the device to device work consists of support of V2x communication, which includes any combination of direct communication between vehicles, pedestrians and infrastructure. V2x communication may take advantage of a NW infrastructure, when available, but at least basic V2x connectivity should be possible even in case of lack of coverage. Providing an LTE-based V2x interface may be economically advantageous because of the LTE economies of scale and it may enable tighter integration between communications with the NW infrastructure (V2I) and V2P and V2V communications, as compared to using a dedicated V2x technology.
For D2D communication there are generally considered retransmission techniques, which may be HARQ techniques or similar thereto, to facilitate correct transmission and reception (respectively decoding) of data.